Clear, cool, sweet running waters, where she, for me the only woman, would rest her lovely body; kind branch on which it pleased her (I sigh to think of it) to make a column for her lovely side; and grass and flowers which her gown, richly flowing, covered with its angelic folds; sacred air serene where Love with those fair eyes opened my heart: listen all of you together to these my mournful, my last words.
You should know something about Petrarch's emotional baggage before reading the Canzoniere. First and foremost, there's Laura, his main squeeze. Petrarch saw her for the first time when she was 17 and could never get her off his mind. But he could also never have her—she was married to someone else and then died while still young. So this explains the longing we see in the first stanza for "she alone who seems lady to me" and all the sorrow and sighing that ensues.
Some people have said that Laura didn't really exist—that "she" was really the personification of poetry (symbolized by the laurel). But Petrarch did write his songs for a particular Laura. And a heart-crushed Petrarch had this to say to a friend who suggested that his lady-love was a figment of poetic imagination: "I wish indeed that you were joking about this particular subject, and that she indeed had been a fiction and not a madness."
In this first stanza (Petrarch uses a Greek type of meter, so the Greek term for stanza, "strophe," is technically the more correct term), it's not clear if the poet is revisiting a place and moment in his memory or if he's really walking around the place. At this point, the narrative situation is this: Petrarch revisits the place on the riverbank (probably the Sorgue in southern France) where he once admired his lady-love. Here, he is assailed by former visions, thoughts, and just a ton of… well, feelings.
But things don't get painful straight off. As you can see from the first line—"Clear, fresh, and sweet running waters"—Petrarch can still admire the natural beauty in the landscape. He praises the brook near which Laura rested her gorgeous body on a spring day. The freshness of the landscape and the charming flowers emphasize his beloved's youth and innocence. There may be some sighing, but that could mean anything at this point.
(Maybe the dude had to climb a hill to get there and now he's out of breath.)
He uses spiritual language in lines 9 and 10 to describe Laura's beauty and purity ("angelic breast") and to explain what she does to the world around her ("sacred bright air"). This language also reinforces the idyllic nature of the place: it's like heaven on earth for peace and visual delight. The grass and flowers take on special beauty—though covered up—because they've come into contact with Laura's clothing. In Petrarch's memory, Laura is saint-like and the epitome of female beauty.
And that's where all happiness ends: right there, in line 12. That's really too bad, since Love personified had just turned up in line 11 to open his eyes to Laura's perfections. The last two lines of this stanza are a direct address to his audience to hang tight—the bad stuff is coming.
Metrically speaking, stanza 1 is a happening place. Check out "Form and Meter" to see how Petrarch works some serious assonance in the "vulgar tongue."